ISSN:
1434-601X
Keywords:
27.90.+ b
;
23.20.Lv
;
23.20.Ck
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The nuclei218, 220, 222Th were investigated by conversion electron andγ-ray spectroscopy after compound nucleus reactions of14N with209Bi and16, 18O with208Pb. The intenseγ-background from fission was suppressed by spectroscopy of conversion electrons andγ-rays in coincidence with the evaporation residues or theirα-decay. Level schemes were determined for218Th up toI π=10+ and for220Th and222Th up toI π=15−. The observed structure of218Th may be explained in the spherical shell model with residual interaction by two neutron excitation. ForN≧130 completely different level schemes are observed showing very intense, collective electric dipole transitions (B(E1)−10−2 W.u.) with energies of typically 200 keV. Interpretation in terms of stable octupole deformations of the ground state as well as in anα-cluster picture are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01412018
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